A pulse radar determines target range by measuring the round-trip time of a pulsed radio frequency (RF) signal, commonly generated through a pulsed oscillator. Pulse repetition frequency (PRF) defines the rate at which radar pulses are sent into air or space. Pulse radar systems find many useful applications in many harsh industrial scenarios such as mining, quarrying, agriculture, construction and waste, that all use very large machines and plant equipment, which by their very nature pose a danger if they are not managed safely. Blind spots tend to be much larger on these applications and include not only the rear and nearside but also the front, especially with elevated driver positions. The pulsed radar installed in these equipments can help to prevent collisions, reduce accidents, fatalities, and injury. Another industrial application of pulse radar is for tank level measurement, where the highest reliability and precision are demanded. It measures the level of liquids, slurries as well as many solids stored inside the industrial tank. One fast growing area for pulse radar is the automotive anti-collision radar system which could significantly enhance road safety for all road users and pedestrians. They aim to warn drivers of potential collisions and alert them to pedestrians or obstacles in blind spots.
There have been some methods and apparatus in achieving an injection locked pulsed oscillator. For example, U.S. Pat. No. 4,320,360, incorporated by reference herein, discloses an injection locked voltage controlled oscillator (VCO) whose phase can be controlled and changed by a series of pulses applied through an isolating element such as a capacitor. This approach, however, is incapable of switching the VCO on and off and thus suffers from high power consumption.
U.S. Pat. No. 4,683,446, incorporated by reference herein, discloses a injection locked pulsed oscillator comprised of a PRF generator, a pulse shaping network, and a pulsed oscillator, where the pulse shaping network reshape a PRF clock signal with fast rising edge to turn on and off the pulsed oscillator through controlling the base of the oscillator transistor. This approach, however, does not provide the tuning ability for center frequency and pulse width.
Other injection locked pulsed oscillators have been described in the following: D. D. Barras et al., “Low-power ultrawideband wavelets generator with fast start-up circuit”, IEEE Trans. Micro. Theory Tech., Vol. 54, No. 5, pp. 2138-2145, March 2006; T. A. Phan et al, “Energy-efficient low-complexity CMOS pulse generator for multiband UWB impulse radio”, IEEE Trans. Circuits Syst. I, Vol. 55, No. 11, pp. 3552-3563, December 2008; N. Deparis et al, “A 2 pJ/bit pulsed ILO UWB transmitter at 60 GHz in 65-nm CMOS-SOI”, in Proc. IEEE Int. Conf. Ultra-Wideband, Vancouver, BC, Canada, pp. 113-117, Sep. 9-11, 2009; all of which are incorporated by reference herein.